checkpointFelipe.js

# W2D2 Checkpoint

Submit a link to your gist [here](https://goo.gl/forms/HywFjkNIU9mLM7c03)

1. Write a function `average` that takes two numbers as input (parameters), and
   returns the average of those numbers.

function average(num1,num2){ // Good Job!
  return (num1 + num2) / 2;
}

2. Write a function `greeter` that takes a name as an argument and *greets*
    that name by returning something along the lines of `"Hello, <name>!"`

function greeter(name){  // Good Job!
  return "Hello, " + name + "! How are you?";
}

3. Write the following functions that each accept a single number as an
   argument:

    + `even`: returns `true` if its argument is even, and `false` otherwise.
    + `odd`: the opposite of the above.
    + `positive`: returns `true` if its argument is positive, and `false` otherwise.
    + `negative`: the opposite of the above.

function even(num1){  // Good Job!
  return num1 % 2 === 0;
}
function odd (num2){ // Good Job!
  return num2 % 2 !== 0;
}
function positive(num3){  // Good Job!
  return num3 > 0;
}
function negative(num4){ // Good Job!
  return num4 < 0;
}

4. Write a function `sayHello` that takes a *language* parameter, and returns
   "hello" in that language. Make the function work with **at least three
   languages**.

function sayHello(language){  // Good Job!
  if(language === "English"){
    return "Hello!";
  }
  if(language === "Portuguese"){
    return "Ola!";
  }
  if(language === "Spanish"){
    return "Hola!";
  }
  return "Unknown language";
}

5. Write a function `validCredentials` that accepts two parameters: *username*
   and *password*, and returns `true` if **both** are long enough, and `false`
   otherwise. You can decide what constitutes "long enough".

function validCredentials(username, password){  // Good Job!
  return (username.length >= 6 && password.length >= 6); // Yeah, bonus points for the one liner :-)
}

6. **Repeating a String `n` Times:** Let's write a function called
   `repeatString` that takes two parameters: a string `str`, which is the string
   to be repeated, and `count` -- a number representing how many times the
   string `str` should be repeated, *e.g.*

function repeatString(str,count){ // OK, good job, but the intention was to make your own, not simply use str.repeat()...
  return str.repeat(count);
}

   ```js
   function repeatString(str, count) {
     // TODO: your code here
   }
   repeatString('dog', 0); // => ''
   repeatString('dog', 1); // => 'dog'
   repeatString('dog', 2); // => 'dog' + 'dog' => 'dogdog'
   repeatString('dog', 3); // => 'dog' + 'dog' + 'dog' => 'dogdogdog'
   ```

7. Write a function called `average` that takes an array of numbers as a
   parameter and returns the *average* of those numbers.

var numbers = [];
function average(numbers){ // Good job, checkout the styling on your for loop, on line 90 - 92, and semicolon on line 91
  var total = 0;
  for (var i = 0; i < numbers.length; i++){
  total = total + numbers[i]
}
return total / numbers.length;
}

8. Write a function `countWords` that, when given a string as an argument,
   returns an *object* where *keys* are the words in the string, and *values*
   are the number of occurrences of that word within the string:

   ```js
   function countWords(s) {
   // ...
   }
   countWords("hello hello"); // => {"hello": 2}
   countWords("Hello hello"); // => {"Hello": 1, "hello": 1}
   countWords("The quick brown"); // => {"The": 1, "quick": 1, "brown": 1}
   ```

   **HINT:** You will want to make use of the string method `split`. Try
   `\"Hello hello".split(" ")` at a console to see how it works.

   - Modify `countWords` to be *case insensitive* by using the following string
     method (experiment at a console with it to learn its behavior):

   ```js
   "HElLo".toLowerCase(); // => ???
   ```
function countWords(s){ // Good Job.
  var words = (s.toLowerCase()).split(" "); // we don't need the () around the s.toLowerCase()...
  var history = {};
  for (var i = 0; i < words.length; i++){
    if(history[words[i]]){
      history[words[i]]++;
    }
    else {
      history[words[i]] = 1;
    }
  }
  return history;
}

   
### Bonus

1. Read about the join method on MDN and use it to implement a function that accepts a string
   as an argument and returns that string reversed.

   function reverseString(str){// Good Job!
    return str.split('').reverse().join('');
   }

2. The function `Object.keys` returns an array of an object's *keys*. Experiment
   with it at the console like this:

   ```js
   Object.keys({a: 1, b: 2});
   ```

   Using this property, write versions of the above functions using repetition
   through function invocation (*i.e.* recursion)